In view of energy saving and reduction in size of an image forming apparatus, there is a demand for a toner that can be favorably fixed through application of less heat to a fixing roller as far as possible. Typically, a toner excellent in low-temperature fixability is prepared using a binder resin having a low melting point or a low glass transition point or a releasing agent having a low melting point. However, in a situation in which such a toner is preserved at high temperature, toner particles included in the toner tend to agglomerate. Once the toner particles agglomerate, the agglomerating toner particle tends to reduce in charge amount when compared to other toner particles that do not agglomerate.
Furthermore, a toner including toner particles each having core-shell structure may be used for the purpose of improving low-temperature fixability, high-temperature stability, and blocking resistance of the toner. For example, Patent Literature 1 discloses a toner including toner particles each having a toner core of which surface is covered with a thin film containing a thermosetting component and of which softening point is at least 40° C. and no greater than 150° C.